With the medicinal substance Fosamprenavir it is a so-called antiviral drug from the family of HIV protein inhibitors. It is used to treat HIV infections and is intended to prevent the development of AIDS (short for: Acquired Immune Deficiency Syndrome). Fosamprenavir is sold under the trade name Telzir® and is sold by GlaxoSmithKline plc. based in London, UK.
What is fosamprenavir?
The active substance fosamprenavir is an antiviral drug. This is a group of drugs that stop viruses from multiplying. The drug belongs to the family of HIV protease inhibitors. This refers to active ingredients that specifically inhibit the activity of the protein-splitting enzymes of the HI virus. In addition to fosamprenavir, this group also includes the preparations nelfinavir and lopinavir.
By preventing protein breakdown, replication of the HI virus is slowed down considerably.
Fosamprenavir is used in tablet form and as a suspension. A suspension is a suspension of small particles that are put into liquid but are not soluble. Medicines containing fosamprenavir require a prescription across Europe. Independent intake without a doctor's prescription is prohibited. In Germany, therefore, there is also a pharmacy requirement.
Pharmacological effect
As an antiviral agent, fosamprenavir inhibits the reproduction of the HI virus in the human body. Unlike bacteria, viruses do not have their own metabolism that could be medically interfered with. This basically makes the therapy of viruses much more difficult. Because the metabolism usually offers an easily accessible attack surface for the destruction of a bacterium.
The drug fosamprenavir therefore works by breaking down protein in the HI viruses contained in the body. The breakdown of proteins (enzymes) is inhibited by fosamprenavir and similar drugs of the HIV protease inhibitors. As a result, no further infectious viruses are formed in the host cell of the body infected by the virus, since HI viruses depend on the enzyme (protease) they produce in order to be able to attack healthy blood cells (CD-4 cells).
Fosamprenavir is broken down or excreted primarily through the liver or stool. The half-life until the active substance is completely eliminated is on average about 7 hours.
Medical application & use
Fosamprenavir is only used in combination with other drugs as part of a comprehensive and medically fully monitored HIV therapy (combination therapy). There is only an indication for the simultaneous use of low-dose ritonavir or similar antiretroviral drugs. Ritonavir increases the levels of the active substance in fosamprenavir.
The recommended daily amount of fosamprenavir is one film-coated tablet with 700 mg of active ingredient twice a day. In addition to these two tablets, the other HIV preparations (e.g. 100 g ritonavir) should be taken. In total, a patient takes four tablets a day (two tablets of fosamprenavir and two tablets of ritonavir). Compared to treatments with the previous drug amprenavir, there is a significant reduction in the number of tablets taken daily.
Fosamprenavir is not used for preventive HIV treatment as part of a so-called PrEP (pre-exposure prophylaxis). The area of application remains limited to combination therapy for HIV.
Risks & side effects
Fosamprenavir must be used together with low-dose ritonavir or other antiretroviral drugs. Only in this way can the pursued purpose be effectively achieved. Every application must therefore be discussed with a doctor or pharmacist. The use of fosamprenavir is prohibited if there is hypersensitivity (allergies) to fosamprenavir, amprenavir or other components of the HIV medication.
Medicines containing fosamprenavir must not be taken with the following preparations:
- Astemizole or Terfenadine (symptomatic treatment of allergies)
- Alfuzosin (treatment of prostate disease)
- Cisapride (treatment for indigestion)
- Pimozide (therapy for schizophrenia)
- Ergotamine derivatives (found in some headache pills),
- Rifampicin (therapy for tuberculosis)
- Propafenone, quinidine, flecainide or amiodarone (preparations for treating diseases of the heart)
- Sildenafil (treatment of erectile dysfunction and diseases of the pulmonary vessels)
- Preparations containing St. John's wort
Fosamprenavir can cause side effects. So far, the following side effects have been reported:
- diarrhea
- Increases in blood cholesterol
- Increased_blood fat levels
- general malaise and feelings of illness (also in connection with nausea, vomiting and abdominal pain)
- Skin irritation (swelling, itching, redness
- a headache
- Dizziness
- fatigue
- Numbness or tingling in the mouth
- increased transaminase and lipase levels
- Facial swelling (especially of the lips or tongue)
- Development of Stevens-Johnson Syndrome. This is a severe skin reaction that can also be life-threatening.
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